Radiator vent operation

ryanr256

I need validation of my understanding of radiator vents on a one-pipe steam system.



Radiator vents are supposed to:



1. close when there's water in the radiator

2. close when the steam heats them up



I ask because none of my vents, 11 radiators in the house, ever close. When the boiler first come on, I can hear the air escaping from the vents. The radiator warms and they are still venting. The radiator eventually gets too hot to touch and the vents are still venting.



I'm assuming all of my vents are bad, which doesn't surprise me because of how the p-trol was set before I cranked it down. I've taken them off and rinsed/cleaned them but it didn't change things.



I have 4 Hoffman 1As, 6 Hoffman 40s and believe it or not a Hoffman 1 on the rad in the garage.



Secondary question - Is it acceptable to replace the 1As with 40s? My thought was to put 40s on every radiator in the house. I don't think we need variable venting and suspect the 1As were installed in an attempt to fix the problems caused by high pressure.



-Bob

BobC

Vents

Your understanding of vent operation s correct.



The hoffman #40 has a small vent rate and may not be suitable for all your radiators. The 40 vents at 0.067CFM (at 2 oz) while the 1A ranges from 0.26CFM (at #1) to 0.225CFM (#6) at 2 oz of pressure.



You might want to take a close look at your radiators and piping to figure out what the venting rate should be for them. You want to vent larger radiators at a faster rate than smaller radiators; any unusually long pipe runs might add to the venting requirement. Adjustable vents allow you to balance the system so things all get hat at the same time. All of this requires that you vent the mains quickly and completely. the main wants to be vented faster than the radiators so the radiator vents only have to handle it's portion of the venting.



How long are your mains and what size pipe? What vents are on them?



What kind of radiator is in each room (how many columns and how many sections)? how long is the pipe that feeds each one and what size pipe is it?



When you have that information we can figure out the cubic footage of air that each vent has to handle.



Bob C

In my system I use Hofmann !A's set from 3 to 6 depending on the volume of air in each radiator and the pipe that feeds it.

TomM

boil' em

boil the vents in half water/half vinegar in a pot on the range.  works for me.  And less birth defects than methylethylketone.

ryanr256

Vent size

Looks like I have some calculating to do.



I'm in the process of measuring for insulation so I'll make a side note for the length of the mains.



The radiators are the water type. I have 3, 4 and 5 tube radiators.



The main comes off of an incorrectly done header and is 2 1/2 inches in diameter. It runs for about 10 feet then there's a two inch T that feeds one side of the house. The T not a bull head T though. The run continues through the T and is necked down to 2 inches to feed the other side of the house. The two feeds then end with the main vents directly over the wet return pipe. One vent is a Hoffman 75 and the other is a Jacobus #1. The Jacobus was used as a replacement for a Hoffman 75 by someone who told me Hofmmans are no longer available. I intended to put another Hoffman on, but I will do the calcs and see what I have.



All radiator feed pies are 1 1/4 inch.



I will do the measuring and get the volume of the pipes/radiators.

For the near boiler piping, I was going to start a new thread with what I have and what I intend to do to replace it with once I had pictures.

-Bob

Big-Al_2

Jacobus Maid-O-Mist

The Maid-O-Mist radiator vents have orifices that can be easily removed and exchanged.  You could buy a variety of them in different sizes, using the chart on their web site, and swap around the orifices until you get the results you want . . . or you could buy all slow ones like #4s or #5s to start out with, and then remove the orifices and drill them out larger on the radiators that you find that could benefit from faster venting.  Just a thought.